Patent GB-673989-A (GB)
Title: Improvements in speed governors
IPC: F02D9/00
Filed: 1949-09-21
Abstract: 673,989. Fluid-pressure servomotor-control systems. FEILDEN, G. B. R., WIGG, R. E., and RUSTON & HORNSBY, Ltd. Sept. 21, 1950 [Sept. 21, 1949], No. 24259/49. Class 135. An engine governor comprises a hydraulic relay having a movable member operative to vary the power output of the governed engine, a pilot valve controlling the operation of the relay, a flyweight system and a speeder spring exerting opposed efforts on the pilot valve, a lever system interconnecting the speeder spring abutment with the movable member of the relay, and the speeder spring abutment is connected by a lead screw and nut device with a member slidable in the body of the governor and pivotally connected to the lever system, and externally operable means are provided for relatively rotating the lead screw and its nut to shift the abutment with respect to the member pivotally connected to the lever system. In a governor for controlling a gas-turbine, the flyweights 55 are driven through a pinion 25 and are provided with rollers 53 acting on a thrust bearing carried by a non-rotatable piston valve 49. The latter controls the flow of pressure oil from an inlet 66 to a passage 69 leading to the working chamber 31 of a cylinder-and-piston power device, and also the exhaust of oil from the working chamber, through passage 69, to a vent port 74. The piston 28 of the power device is directly connected to the fuel valve 34 controlling the engine, the valve being provided with metering notches 36. The speeder spring 50 acts on the end of valve 49 remote from the flyweights, and it also abuts against a cup 114 keyed in a thimble 115. A leadscrew 117 has a threaded connection with the cup 114 and also carries a pinion 118 in engagement with a screw 119 whereby rotation of screw 119 causes cup 114 to advance or retreat in the thimble and so set the speeder spring to give the datum speed at which the governor will control the engine. A repeatback from the piston 28 on to the speeder spring is provided by a lever 123 which is connected to the stem of the piston at 124, pivotally connected to the thimble 115 by pins 122, and also pivoted by trunnions 127 on the arms of a yoke-like member. This yoke can be adjusted in position and the trunnions 127- which can slide up and down guides in the lever 123-may thus be positioned above the pins 122 to give various degrees of droop to the governor characteristic, i.e. governed speed decreasing with increase of load, or be positioned below the pins 122 to give a rising characteristic. A pair of helical springs 132 acting on the lower end of lever 123 constitute the return springs of the piston 28. The sensitivity of the governor can be varied by means of an adjustable bleed 100 from passages 69, 98 which are connected to the working space 31 of the power device. Surrounding piston valve 49 is a follow-up, cylindrical sleeve valve 47 which is connected to the flyweights by laminated springs 57 and rotates therewith, and its other end is acted upon by a spring 63. Movements of the piston 28 are repeated back to the valve 47 by means of a hydraulic link, the latter being made up of a space 32 enclosed between the piston 28 and a sealing bellows 30, a passage 62, and the space 61 between the free end of valve 47 and a fixed abutment 48 surrounding piston valve 49. This hydraulic link communicates through a passage 104 with a variable volume reservoir of which one wall consists of a bellows loaded by an adjustable leaf spring. An adjustable bleed 101 from this hydraulic link, in combination with the springs loading valve 47, ensure that the speed droop produced by the governor is only temporary. An adjustable eccentric pin constitutes a stop for lever 123, and thus for the fuel valve 34, to limit the extent to which the fuel valve can be closed by the governor when the engine is running under no-load conditions. The end of valve 49 adjacent the speeder spring is also formed as a valve head which, when moved to the right, vents a space 80 in a conduit leading from the pressure inlet 66, through radial passages and a bore 78 in piston valve 49, radial passages 83 in sleeve valve 47, and an outlet 85, to a compressor blow-off valve. Thus, if the engine overspeeds suddenly, the piston valve 49 will be moved sufficiently to vent the space 80 and the engine will be shut down. The free end of the bore 78 is partially closed by a restrictor 88 which allows the flow of sufficient oil to lubricate the thrust bearing 52.